I don't mean to be a jackass, but... duh? If you're using GoDaddy's nameservers, it stands to reason that you'd need to configure the new ones when namecheap isn't going to be able to point to a defunct GoDaddy account.
Gandi will even offer to mirror the DNS on import.
Agreed, it was a dumb mistake. I just wanted to let others know so they don't have to suffer the consequences as well of multiple hours of downtime waiting for things to finalize before you can change it.
Heh, sorry, didn't know this was spurred by a necessity. I'm one of those guys that researches things to death before I do them, even if my "liability" is 3 low traffic family email accounts in a domain registrar migration.
Gandi will even offer to mirror the DNS on import.